Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 402

capacitance was not determined. Tesla's own doubts about this way of determining the secondary in terms of length of wire are best revealed when he refers to checking its resonant frequency treating it as an oscillatory circuit.

June 21

Returning once more to the problem of the conversion of mains power into HF power Tesla calculates the energy in each charging cycle of the condenser (see comments for June 20th). Taking it that all the energy in the charge condenser will at some instant be found in the condenser of the secondary circuit, he in fact works out the peak voltage on the secondary condenser. The energy equation for lossless coupled circuits has the general form

$!{1 \over 2}$! C_pU²_p = $!{1 \over 2}$! C_sU²_s

where p refers to the primary, s to the secondary circuit, U is peak voltage. It should be noted that Oberbeck's theory⁽²⁹⁾ yields the same ratio between the voltage on the primary condenser just before discharge begins and the peak voltage on the secondary condenser.

June 22

The circuit with two condensers, one being charged from the power supply and the second via a spark from the first represents a modification of Tesla's classic oscillator*. Theory shows that protraction of the oscillation in the primary circuit lowers the efficiency of the oscillator because energy pulses back and forth between the primary and secondary. However, in this circuit protraction of the spark does not have the same effect because while it lasts the primary capacitance is C + C₁, but when it stops the capacitance is only C₁. Why the sparks in the secondary were stronger with C = aC₁, a a whole number, is hard to say without a more exhaustive analysis.

The note at the end of the entry indicates his satisfaction with the results and that he felt it necessary to continue research in the same direction.

June 23

The two formulae are in fact identical if the thickness of the wire is neglected, because then

£² = (2πrN)² = 4πSN²

June 24

Rarefied gases had long interested Tesla, and his work on their conducting properties, especially at high frequencies, is well known, e.g. the patents on an electric lighting system and an incandescent lamp⁽³⁷⁾. He presented detailed analyses of the same problems in his famous lectures^{(4, 5, 6)}. Rarefied gas as a conductor is also referred to in his patent application “System of transmission of electrical energy”⁽¹³⁾.